The Faint Object Spectrograph Red detector onboard the HST is now being
used for the first time in ACQIMAGE mode with the large barred aperture to
search for suspected companions to six cool stars in the solar neighborhood
(HST proposal 6059). The FOS is ideal for detecting faint companions
because of its large dynamic range, sensitivity, sub-arcsecond resolution,
and low detector noise. The limiting magnitude of the FOS ACQIMAGE mode
is mv= 22.

An ACQIMAGE is created when the FOS camera mirror images the aperture onto
the photocathode. An on-orbit stellar image is rectangular because of the
shape of the mapping diodes (0.31"x1.29"). Deconvolution is used to
produce a final image scale of 0.08"/pixel. Preliminary modeling indicates
a companion can be detected as close as 0.2" for a system of nearly equally
bright stars, and as close as 0.8" if the magnitude difference between the
primary star and its companion is ten magnitudes.

Two stars with known companions are included in the program in order to
verify the new target location and imaging techniques. The other four
stars have suspected companions. This paper is a report on the feasibility
of this unique imaging capability, with preliminary results for Cycle 5
targets GL293 (successfully observed in September 1995) and GL1245AC
(scheduled to be observed in December 1995).